The proposed research will deal with aspects of the control of enzyme concentration levels in mammalian cells and some related topics in protein chemistry and enzymology: (a) Glycogen phosphorylase is controlled primarily at the activity level. The liver enzyme differs from the muscle enzyme, is less well characterized, and more likely to exhibit concentration variations. We propose to complete its purification, describe its properties more fully, and to investigate the nutritional and hormonal factors that affect it rates of synthesis and degradation. (b) The glyceraldehyde-3-phosphate-dehydrogenase of liver and muscle occur in multiple forms which we now believe not to be artifacts. We propose to identify the structural differences and to determine their functional significance. (c) The sucrase of intestinal brush border membranes can be solubilized and purified. We have found it to be strongly inducible. We propose to examine in more detail its structure and properties, its function as a membrane-bound protein, its metabolism as a glycoprotein, and aspects of its induction. (d) In parallel with some of the above work, we will continue exploratory collaborative work on applications of Fourier transform NMR spectroscopy in the study of segmental motions of enzymes in solution.